In a long-term evolution (LTE) system, a user equipment (UE) obtains channel state information (CSI) in downlink by measuring a downlink reference signal, and reports to a base station via an uplink, the CSI comprising a channel quality indicator (CQI) of the downlink, and also information of precoding matrix indicator (PMI) and rank indication (RI) for some downlink transmission mode. The above CSI, as well as ACK/NACK information and scheduling request (SR), are collectively referred to as uplink control information (UCI). The UCI may contain one piece of the above information only, or more pieces of the above information. The base station selects typical modulation and coding scheme, multi-antenna processing and hybrid automatic repeat request (HARM) on the basis of the UCI reported by the UE, and adaptively adjusts data transmission dynamically.
Currently, the CSI in the UCI may be reported periodically and aperiodically. Here, for the sake of convenience, the CSI reported periodically is referred to as periodic CSI, and the CSI reported aperiodically is referred to as aperiodic CSI. Generally, UCI containing periodic CSI is transmitted on a physical uplink control channel (PUCCH), and UCI containing aperiodic CSI is transmitted on a physical uplink shared channel (PUSCH), which may be multiplexed with uplink data (such as UL-SCH (uplink shared channel) data), and may also be transmitted separately on a PUSCH when there is no uplink data.
When it is necessary for a UE to report aperiodic CSI, the following manner may be used: when a base station requires a user equipment to report aperiodic CSI, the base station transmits downlink control information (DCI) to the UE, so as to instruct the UE to report aperiodic CSI and allocate corresponding PUSCH resources used for reporting the aperiodic CSI to the UE; when the UE receives the DCI, it reports aperiodic CSI by using the resources instructed in the DCI, and has the CSI contained in the UCI and transmitted to the base station via the PUSCH.
In an LTE system, one bit in a DCI format 0 is used to trigger a UE to report aperiodic CSI. In an advanced long-term evolution (LTE-A) system, since the system may support the transmission of multiple component carriers (CCs), and may support at most five CCs at present, so, in order to instruct a UE to report UCIs of multiple downlink CCs flexibly, two bits in DCI format 0/DCI format 4 are used to trigger a UE to report aperiodic CSI, and the UE is indicated to report the indices and the number of the corresponding downlink CCs.
In the implementation of certain embodiments, this applicant found that following defects exist in the prior art:
In an LTE system, each UE is configured with only one pair of uplink and downlink CCs. When the UE transmits UCI containing aperiodic CSI on a PUSCH with no data, a base station allocates four resource blocks (RBs) to the UE at most, and ensures the correct receiving of the UCI containing aperiodic CSI by using a reasonable channel encoding rate.
However, in an LTE-A system, with the number of CCs increases, the length of the UCI also increases. If the base station allocates four RBs to the UE at most, the resources allocated by the base station to the UE for transmitting the UCI containing aperiodic CSI are possibly insufficient. Hence, the correct receiving of the UCI by the base station cannot be ensured, and limitation of the scheduling of the data transmission by the base station is increased. No solution has been found till now to overcome the above defects.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of certain embodiments herein and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art.